Systems are used analyzing organic samples by way of combusting a sample and analyzing the gaseous products. For example, U.S. Pat. No. 3,252,759 (Simon) discloses a system in which gaseous combustion products are drawn into an enclosed reservoir that had been previously evacuated. The gas mixture is then released into a second evacuated vessel by way of a series of detectors that sequentially determine the amounts of such combustion product components as water and carbon dioxide in the mixture. Each detector comprises a pair of thermal conductivity measuring devices. The component being measured is removed from the gas mixture between the first and second devices in the pair, and the difference between the measurements, with calibration, provides the amount of the constituent.
U.S. Pat. No. 3,698,869 (Condon) avoids alleged problems of the Simon system, with its vacuum requirements, by operating above atmospheric pressure. The combustion products are mixed with and forced under the pressure of an inert carrier gas into a reservoir. A pressure switch in a gas line leading out of the reservoir shuts a valve between the combustion train and the reservoir. The gas mixture from the reservoir is then passed into a "delay volume" in the form of a coiled tube. Time periods are successively allowed in both the reservoir and the "delay volume" to complete mixing of the gases. The mixture in the "delay volume" is then shut off from the reservoir and forced from the "delay volume" through a series of detectors at constant pressure by the carrier gas source and vented to atmosphere. The detectors are of the type disclosed in Simon and vented to atmosphere. Although the Condon system has proven to be quite practical and successful, there is still a substantial need for increased speed of operation, accuracy and simplification of operation.
A modified technique is taught in "Frontal Gas Chromatography as an Analytical Tool" by Vlastimil Rezl and Jitka Uhdeova, American Laboratory, January 1976, Pages 13-26. A chromatographic column formed of a coiled tube containing gas adsorption material is substituted for the "delay volume" tube, and a single detector receives the flow output from the column. Gas components are successively adsorbed. The heights of the adsorption steps of the components displayed from the detector signal are used (again with calibration) to provide the quantitative analysis. Rezl et al. describe the technique in a system that involves constant pressure flow through the column, achieved with a dilution chamber containing an easily movable piston maintained under constant gas pressure from the back side. The Rezl system involves a substantial degree of complexity of gas lines and valving.
Related concerns to improve operating efficiency exist with respect to introducing samples of solid material into a system for analysis. It is desirable to have an apparatus for loading the samples into the furnace with a minimum of time and dead volume of gas, and with a simple, efficient system for sealing from the ambient atmosphere.
U.S. Pat. No. 4,055,259 (Sibrava) discloses a sample transport apparatus for conveying test samples horizontally from a source into a combustion chamber. Samples are initially contained in a motor driven rotary magazine. A sample is dropped from the magazine into an aperture in a motor-driven rotary transfer plate. The plate is rotated a half turn to drop the sample through a passage onto a sample transport member. The sample transport member rides horizontally into a conduit which extends to the furnace. The sample transport member is conveyed to the furnace by means of a motor-driven tape. A reversed procedure is used to withdraw and drop the solid remnants of combustion through a second rotary plate and a second passage out of the apparatus. Sealing of the various orifices is accomplished by means of O-rings on which the sample plates ride.
Sample introduction into a vertically aligned furnace is disclosed in U.S. Pat. No. 4,525,328 (Bredeweg). A set of jaws is displaced horizontally to grab a sample, which is then moved over to the top of the furnace inlet and released by the jaws.
The above-described transport devices are workable in varying degrees but suffer from the complexity of motors or interconnecting gears (or pulleys) and from the unreliability of sliding seals.
Therefore, an object of the present invention is to provide an improved apparatus and method for analysis of gaseous mixtures.
Another object is to provide a novel gas analysis apparatus having improved speed of operation, accuracy and simplification of operation.
Yet another object is to provide an improved system for analysis of organic samples by analyzing gaseous combustion products.
A further object is a novel system for rapid transfer of samples into a testing apparatus with reliable sealing against ambient atmosphere.